The present invention relates to a thin film magnetic head mounted on a magnetic disk apparatus and used for reading/writing data, a manufacturing method thereof, and a magnetic disk apparatus using the thin film magnetic head. More specifically, the invention relates to a magnetic pole-forming technique for improving the recording characteristics of a thin film magnetic head with regard to the material and manufacturing method thereof.
Higher data communication speed and higher recording density have been demanded for magnetic disk apparatuses. To meet this demand, a recording medium is needed that has a high coercivity, as is a thin film magnetic head capable of recording at a higher frequency applicable to higher speed communication, using a material of low coercivity in the direction of difficult magnetization of the axis (hereinafter referred to as Hc) or a low anisotropic magnetic field (hereinafter referred to as Hk), in view of the requirement for reducing hysteresis in the magnetic poles. Further, a material of high specific resistivity (hereinafter referred to as ρ) has been needed in view of the requirement for reducing an eddy current loss. Further, recording characteristics for the high coercive medium have been improved to attain high recording density using a material having high-saturation magnetic flux density (hereinafter referred to as Bs).
Heretofore the magnetic pole, 52-58 wt % FeNi series alloy plating (Hk 5 to 10 Oe, Bs 1.65 to 1.75 T) having low Hc (1.0 to 1.5 Oe) and high ρ (40 to 50 μΩ cm) was used for the core portion, and a CoNiFe series alloy plating (Hc 10 to 25 Oe, Hk 15 to 25 Oe, ρ 15 to 20 μΩ cm) having high Bs (2.0 to 2.4 T) was used near the gap. For the high Bs material, it has been reported that Bs was 2.OT or more in the CoNiFe series in JP-A No. 2002-217029 and in the NiFe series alloy plating in JP-A No. 2002-208514 and this was already known in view of presentation and products from manufacturers of thin film magnetic heads.
For further higher speed and high recording density of magnetic disk apparatuses, materials capable of further reducing the hysteresis loss and the eddy current loss in the high-frequency recording band and having high Bs characteristics have to be used for the magnetic pole portion of the thin film magnetic head.
Further, the magnetic pole portion generates heat during recording operation, that is, during generation of the magnetic recording fields of the thin film magnetic head due to the hysteresis loss and the eddy current loss. The heat generation involves a problem of thermal protrusion. The magnetic pole portion expands thermally protruding in the direction of a recording medium or further, causing a collision due to heat generation. This problem hinders the low flying height of the thin film magnetic head, which is a focal subject of hindering higher speed and higher recording density of magnetic disk apparatuses.
As can be seen from the data described above, in the prior art, the 52-58 wt % FeNi series alloy plating material has the drawback of high Hk and small Bs despite the low Hc and high ρ, whereas the CoNiFe series alloy plating material has the drawback of high Hc, high Hk and low ρ although having high Bs. The FeNi series alloy has the merit of peaking at ρ40-50 μΩ cm in an Fe compositional region of 52 to 58 wt % and Bs increases while ρ lowers in a further Fe-rich region (range where Fe is 60 wt % or more). However, in Fe≧60 wt %, a problem arises causing whitening or blackening due to plating surface roughness, leading to the failure of the product.
On the other hand, for the CoNiFe series alloy, since the crystal structure has a bcc structure in most of compositional regions having Bs≧1.8 T, lowering of Hc due to the bcc structure is impossible. Although an fcc structure had been developed by modification of the composition, the phenomenon of surface roughness occurred as in the FeNi series alloy described above and development had to be given up. A thin film magnetic head capable of overcoming such a difficulty, as well as a manufacturing method thereof have not yet been provided.